I remember alert without console.log as well but I was too young to understand the context.
For ios mobile dev I use Safari as a debugger. If I have to use Chrome, I basically use a scrappy console that I made on the HTML page itself.
Be careful about using JSON.stringify on objects as a debugging technique though, because you may not be able to see properties on the prototype chain ('inherited' properties), and some objects customize their serialization to JSON (supply a custom toJSON method) which in some cases can be misleading. Things like that have contributed to a number of my grey hairs. Yes, I'm talking about you, Geolocation Coordinates! :)
Chrome has really nice support for remote debugging on Android.
If you can't get physical access to the device to configure them for remote debugging, there are some other nice remote debugging tools. One example: https://jsconsole.com/remote-debugging.html
Back in the day when I was working on the Sage Notebook, there weren't good javascript consoles. I can't recall if Firefox had one at the time (around 2007, I think), but it was certainly missing from Safari, IE, and Opera. But, it was an interactive notebook -- so I hijacked the "input cell" we were using to concoct what was essentially a console.
Thank god I don't have to support IE anymore, what a mess it was.